This year, toxicity of chloroform has been demonstrated to be a free radical mechanism dependent on: 1) rate of biotransformation; 2) availability of glutathione. Studies with other halogenated anesthetics (halothane, fluroxene, enflurane) will be conducted to ascertain if evidence of free radical mechanisms exist. The assay of lipid extractable lipofusbin fluorescence pigments (as evidence of free radical pathology) will continue. This technique will be perfected such that it may be employed eventually as a differential diagnosis of cause of hepatic injury in man. Enzymatic mechanisms of volatile anesthetic metabolism are in progress both in vivo and in vitro. Methoxyflurane is definitely a cytochrone P-450 substrate; halothane is not. Trichloroethylene appears similar to methoxyflurane. Enflurane will also be studied in this regard. Relative dependency on NADPH and NADH for reducing equivalents will be performed. Effects of NADPH cytochrome c and cytochrome b5 inhibition by Subtilism VII will be examined. Kinetics of binding are also in progress. Inhalation anesthetics inhibit fixed drug metabolism both in vivo and in vitro. Mechanisms of this inhibition are in progress with each electron transport carrier in the system. Saturation in vitro kinetics of methoxyflurane metabolism are almost completed. These studies indicate methoxyflurane is not a substrate inhibitor. Rate constants are being determined. Other anesthetics will be studied in similar manner.